JP2025147594A - Microfluidic Devices - Google Patents

Abstract

To provide a microfluidic device that can uniformly culture hepatocytes at high density and efficiently collect excreted bile.SOLUTION: A microfluidic device 1 comprises: a device body 2 having an upper surface 2a and a lower surface 2b; a first recess 3 for culturing cells and a second recess 4 for supplying or discharging a fluid, which open on the upper surface 2a of the device body 2 at positions spaced apart in a first horizontal direction D1 parallel to the upper surface 2a of the device body 2; and a microchannel 5 connecting the bottom surface 3a of the first recess 3 with the bottom surface 4a of the second recess 4. The microchannel 5 comprises a plurality of first grooves 51 formed at least on the bottom surface 3a of the first recess 3 and aligned in a second horizontal direction D2 perpendicular to the first horizontal direction D1.SELECTED DRAWING: Figure 2

Description

The present invention relates to a microfluidic device.

The use of microfluidic devices with microchannels has been proposed to cultivate hepatocytes and collect and analyze the bile excreted from the hepatocytes. For example, Patent Documents 1 and 2 listed below disclose a bile collection chip in which a tubular microchannel has a region for culturing hepatocytes with comb-like irregularities on the bottom surface, and a well that can introduce or discharge culture medium is connected to the microchannel, with the irregularities extending to a collection port that collects bile.

Japanese Patent Application Laid-Open No. 2023-20221 International Publication No. 2022/118885

However, it has been difficult to culture hepatocytes uniformly and at high density on the uneven portions of tubular microchannels. This is because, as the amount of culture medium is limited when using microchannels, it is necessary to use a culture medium with a high cell density. However, when trying to introduce a cell-dense liquid into a microchannel, high fluid resistance makes injection difficult, and the cells disperse unevenly during the injection process, resulting in variations in cell distribution after seeding. Furthermore, although it is desirable to limit cell culture to the uneven portions, cells are seeded throughout the microchannel, and cells outside the uneven portions must be removed. Furthermore, the removed cells are discarded, which increases costs when culturing expensive cells.

In view of the above-mentioned problems, the present invention aims to provide a microfluidic device that can culture hepatocytes uniformly and at high density and efficiently collect excreted bile.

The microfluidic device of the present invention comprises: a device body having an upper surface and a lower surface;
a first recess for culturing cells and a second recess for supplying or discharging a fluid, the first recess and the second recess opening on the upper surface of the device body at positions spaced apart in a first lateral direction parallel to the upper surface of the device body;
a microchannel communicating a bottom surface of the first recess and a bottom surface of the second recess,
The microchannel includes a plurality of first grooves formed at least on the bottom surface of the first recess and aligned in a second horizontal direction perpendicular to the first horizontal direction.

With this configuration, the first groove, which is part of the microchannel, is formed on the bottom surface of the first recess for culturing cells, allowing hepatocytes to be reliably seeded on the microchannel and cultured uniformly and at high density on the microchannel. Furthermore, because bile excreted from hepatocytes flows into the first groove, the excreted bile can be discharged from the second recess via the microchannel and efficiently collected.

Furthermore, in the microfluidic device according to the present invention, the microchannel may be configured to include a plurality of holes formed between the first recess and the second recess, aligned in the second horizontal direction, and connected to the first horizontal ends of the plurality of first grooves, respectively.

This configuration allows bile that flows into the first groove to be properly guided to the second recess through the hole.

In the microfluidic device according to the present invention, the microchannel includes a plurality of second grooves formed in a bottom surface of the second recess and aligned in a second lateral direction,
The second grooves may be connected to the first lateral ends of the holes, respectively.

This configuration allows bile that flows into the first groove to be properly guided to the second recess via the hole and the second groove.

In addition, in the microfluidic device according to the present invention, the first recess may be configured to include a lower space extending upward from the bottom surface, a step portion at the upper end of the lower space that has a larger cross-sectional area than the lower space, and an upper space adjacent to the upper side of the lower space and whose cross-sectional area is enlarged by the step portion.

With this configuration, the lower space is recessed, making it easy to seed hepatocytes in the lower space and allowing them to be cultured at high density. Furthermore, because the upper space is larger than the lower space, hepatocytes can be cultured in the lower space while perfusing culture medium in the upper space.

In the microfluidic device according to the present invention, a plurality of the first recesses and a plurality of the second recesses are provided along a second lateral direction,
The lower spaces adjacent to each other may be independent from each other, and the upper spaces adjacent to each other may be connected to each other.

With this configuration, culture medium can be perfused through a single upper space for multiple first wells, allowing cells to be cultured efficiently.

Furthermore, in the microfluidic device according to the present invention, a plurality of the first recesses may be provided independently of each other along the first horizontal direction.

This configuration allows cells to be cultured simultaneously in multiple first wells, allowing cells to be cultured efficiently.

Furthermore, in the microfluidic device according to the present invention, a plurality of the second recesses may be provided so as to sandwich the first recess in the first horizontal direction.

With this configuration, for example, liquid can be supplied to one second recess and discharged from another second recess while collecting excretory substances such as bile.

Furthermore, in the microfluidic device according to the present invention, the plurality of first grooves may be formed over the entire bottom surface of the first recess.

With this configuration, the area where cells are cultured can be limited to above the multiple first grooves, allowing hepatocytes to be cultured at high density.

1 is a perspective view of a microfluidic device according to an embodiment of the present invention; 1 is a plan view of a microfluidic device according to an embodiment of the present invention; 3 is a cross-sectional view of the microfluidic device shown in FIG. 2 taken along line III-III. IV-IV cross-sectional view of the microfluidic device shown in FIG. A cross-sectional view of the microfluidic device 1 shown in FIG. 2 taken along line VV. 6 is a cross-sectional view of the microfluidic device 1 shown in FIG. 2 taken along line VI-VI. A perspective view of a first substrate A perspective view of a second substrate A perspective view showing an example of how to use a microfluidic device. 1 is a plan view of a microfluidic device according to another embodiment; 1 is a plan view of a microfluidic device according to another embodiment; 1 is a plan view of a microfluidic device according to another embodiment; 1 is a plan view of a microfluidic device according to another embodiment; 1 is a plan view of a microfluidic device according to another embodiment; 1 is a plan view of a microfluidic device according to another embodiment; 1 is a plan view of a microfluidic device according to another embodiment; 1 is a plan view of a microfluidic device according to another embodiment;

The microfluidic device according to the present invention will be described with reference to the drawings. Note that the drawings disclosed in this specification are merely schematic illustrations. In other words, the dimensional ratios shown in the drawings do not necessarily match the actual dimensional ratios, and the dimensional ratios between the drawings do not necessarily match.

Figure 1 is a perspective view of a microfluidic device 1 according to this embodiment, and Figure 2 is a plan view of the microfluidic device 1 according to this embodiment. Figure 3 is a cross-sectional view of the microfluidic device 1 shown in Figure 2 taken along line III-III, Figure 4 is a cross-sectional view of the microfluidic device 1 shown in Figure 2 taken along line IV-IV, Figure 5 is a cross-sectional view of the microfluidic device 1 shown in Figure 2 taken along line V-V, and Figure 6 is a cross-sectional view of the microfluidic device 1 shown in Figure 2 taken along line VI-VI.

The microfluidic device 1 includes a device body 2 having a substantially rectangular parallelepiped shape. The device body 2 has an upper surface 2a and a lower surface 2b that face each other in the vertical direction D3. In this embodiment, the upper surface 2a and the lower surface 2b are rectangular. In the following description, the horizontal direction parallel to the upper surface 2a and along one side of the upper surface 2a is referred to as the first horizontal direction D1, and the horizontal direction parallel to the upper surface 2a and perpendicular to the first horizontal direction D1 is referred to as the second horizontal direction D2.

The microfluidic device 1 has a first recess 3 and a second recess 4 that open on the top surface 2a of the device body 2. The first recess 3 and the second recess 4 each have a bottom surface 3a, 4a that is located midway in the vertical direction D3 of the device body 2. The first recess 3 and the second recess 4 each also have openings 3b, 4b that are located on the top surface 2a of the device body 2.

The first recess 3 and the second recess 4 are arranged side by side in the first horizontal direction D1. The first recess 3 and the second recess 4 are also arranged at a distance from each other. In other words, the opening 3b of the first recess 3 and the opening 4b of the second recess 4 can be said to be arranged at a distance from each other.

The first recess 3 is used for seeding and culturing cells. The second recess 4 is used for supplying or discharging liquid to or from the microfluidic device 1. In this embodiment, two second recesses 4 are provided, sandwiching the first recess 3 in the first horizontal direction D1. For example, liquid is supplied to one second recess 4 and discharged from the other second recess 4.

As shown in Figure 3, the first recess 3 comprises a lower space 31 extending upward from the bottom surface 3a, and an upper space 32 adjacent to the upper side of the lower space 31 and having a larger cross-sectional area than the lower space 31. The first recess 3 comprises a step portion 33 at the upper end of the lower space 31 that has a larger cross-sectional area than the lower space 31, and the cross-sectional area of the upper space 32 is enlarged by this step portion 33.

The bottom surface 3a is square-shaped, as shown in FIG. 2, although not limited thereto. The lower space 31 extends upward from the bottom surface 3a with a constant cross-sectional area. The opening 3b is wider than the bottom surface 3a and is located further outward than the bottom surface 3a in a plan view. The opening 3b is generally elliptical, as shown in FIG. 2, although not limited thereto. The upper space 32 extends downward from the opening 3b with a constant cross-sectional area. The opening 3b is formed so that its width in the second horizontal direction D2 is greater than its width in the first horizontal direction D1. As a result, the distance from the lower space 31 to the second horizontal direction D2 of the step portion 33 is greater than its distance in the first horizontal direction D1.

The lower space 31 has a width of 4 mm in the first horizontal direction D1, a width of 4 mm in the second horizontal direction D2, and a height of 3 mm in the vertical direction D3. The upper space 32 has a width of 6 mm in the first horizontal direction D1, a width of 12 mm in the second horizontal direction D2, and a height of 5 mm in the vertical direction D3. The width of the upper space 32 in the second horizontal direction D2 is set to the maximum width at which the curve in the second horizontal direction D2 widens the widest.

The bottom surface 4a of the second recess 4 is generally elliptical, although not limited to this, as shown in Figure 2. The second recess 4 extends upward from the bottom surface 4a with a constant cross-sectional area. As a result, the opening 4b overlaps the bottom surface 4a in a plan view. The second recess 4 has, for example, a width of 2 mm in the first horizontal direction D1, a width of 6 mm in the second horizontal direction D2, and a height of 8 mm in the vertical direction D3. The width of the second recess 4 in the second horizontal direction D2 is set to the maximum width at which the curve in the second horizontal direction D2 widens to its widest.

As shown in Figures 2 and 6, the microfluidic device 1 has a microchannel 5 that connects the bottom surface 3a of the first recess 3 and the bottom surface 4a of the second recess 4. The microchannel 5 extends in the first lateral direction D1.

The microchannel 5 has a plurality of first grooves 51 formed on the bottom surface 3a of the first recess 3. The plurality of first grooves 51 are aligned in the second horizontal direction D2. The plurality of first grooves 51 are preferably formed across the entire bottom surface 3a of the first recess 3. In this embodiment, as shown in FIG. 2, the plurality of first grooves 51 are formed across the entire bottom surface 3a in the first horizontal direction D1 and across substantially the entire bottom surface 3a in the second horizontal direction D2.

In this embodiment, the cross section of the first groove 51 is rectangular. However, the cross section of the first groove 51 is not limited to a rectangular shape and may be a trapezoid or semi-ellipse whose width narrows toward the bottom of the groove.

The width of the first grooves 51 (width in the second horizontal direction D2) is, for example, 3 to 100 μm, and in this embodiment, 5 μm. The depth of the first grooves 51 (height in the vertical direction D3) is, for example, 5 to 150 μm, and in this embodiment, 10 μm. The spacing between the first grooves 51 is 1 to 2 times the width, and in this embodiment, 20 μm. There may be, for example, 20 to 1,000 first grooves 51, but in this embodiment, only 13 are shown for ease of explanation.

The microchannel 5 also has a plurality of second grooves 52 formed on the bottom surface 4a of the second recess 4. The plurality of second grooves 52 are aligned in the second horizontal direction D2. The width of the second grooves 52 (width in the second horizontal direction D2) is, for example, 3 to 100 μm, and in this embodiment, it is 5 μm. The depth of the second grooves 52 (height in the vertical direction D3) is, for example, 5 to 150 μm, and in this embodiment, it is 10 μm. The spacing between the second grooves 52 is 1 to 50 times the width, and in this embodiment, it is 20 μm. The spacing width is selected depending on the adhesiveness of the cells used.

The microchannel 5 also has a plurality of holes 53 formed between the first recess 3 and the second recess 4. The holes 53 are aligned in the second horizontal direction D2. The holes 53 are connected to the ends of the first grooves 51 in the first horizontal direction D1, respectively. The second grooves 52 are also connected to the ends of the holes 53 in the first horizontal direction D1, respectively.

It is preferable that the first groove 51, second groove 52, and hole 53 all have the same cross-sectional shape and are connected to each other. This means that the bottom and side surfaces of the first groove 51, second groove 52, and hole 53 are continuous with no steps, so the flow of liquid is not obstructed. The length of hole 53 is, for example, 2 mm. Holes 53 may also be connected to adjacent holes. This reduces fluid resistance within the holes and improves the flow of liquid.

The device body 2 of this embodiment may also include a first substrate 21 as shown in FIG. 7 and a second substrate 22 as shown in FIG. 8 that is arranged in partial contact with the upper surface of the first substrate 21. In other words, the microfluidic device 1 may be formed by stacking and bonding the second substrate 22 so that the lower surface of the second substrate 22 is in partial contact with the upper surface of the first substrate 21. An example of a method for manufacturing such a microfluidic device 1 is described below.

(Substrate preparation process)
First, a first substrate 21 and a second substrate 22 are prepared, which constitute the microfluidic device 1. At this stage, the first substrate 21 and the second substrate 22 are, for example, rectangular plate-shaped members.

The first substrate 21 and the second substrate 22 are preferably made of a substantially non-porous material. Here, "substantially non-porous" refers to a state in which the apparent surface area of the substrate is close to its actual surface area. Examples of materials that form such non-porous bodies include inorganic materials such as glass and silicon, and resin materials such as polymethyl methacrylate (PMMA), polycarbonate (PC), cycloolefin copolymer (COC), cycloolefin polymer (COP), polystyrene (PS), and silicone. Two or more of these resin materials may be combined. The materials used for the first substrate 21 and the second substrate 22 may also be different.

(Shape processing of first substrate 21)
Lithography is used to etch the first substrate 21 to a fine depth in regions where the first groove 51, the second groove 52, and the holes 53 are to be formed. This etching depth is set according to the depths of the first groove 51 and the second groove 52 and the height corresponding to the diameter of the holes 53, as described above. If the first groove 51, the second groove 52, and the holes 53 have the same cross-sectional shape, this processing will form the uneven groove 21a over the entire region where the microchannel 5 is to be formed. Thereafter, the second substrate 22 is bonded to the upper surface of the first substrate 21, and as a result, the uneven groove 21a is partially covered by the second substrate 22, and multiple holes 53 are formed.

(Shape processing of second substrate 22)
The through holes 22a and 22b are formed in the second substrate 22 in the areas where the first recess 3 and the second recess 4 are to be formed by injection molding, cutting, or other methods.

(Joining process)
The first substrate 21 and second substrate 22 thus shaped are bonded together to obtain the microfluidic device 1 shown in Fig. 1. Bonding methods that can be used include bonding using surface modification using light or plasma, thermal bonding, adhesion using an adhesive, and bonding using a solvent. An example of a bonding method is as follows.

First, a surface activation process is performed on the bonding surfaces of the first substrate 21 and the second substrate 22. The surface activation process can be performed by irradiating them with ultraviolet light. Specifically, this process is performed by irradiating them with vacuum ultraviolet (VUV) light having a wavelength of 200 nm or less from an ultraviolet light source. Suitable ultraviolet light sources include a Xe excimer lamp with a peak wavelength of approximately 172 nm, a low-pressure mercury lamp with an emission line at 185 nm, and a deuterium lamp with an emission line in the wavelength range of 120 to 200 nm. The irradiance of the vacuum ultraviolet light is, for example, 10 to 500 mW/ ^cm² , and the irradiation time is set appropriately depending on the materials forming the first substrate 21 and the second substrate 22, but is, for example, 0.1 to 60 seconds.

Next, the bonding surfaces of the first substrate 21 and the second substrate 22, which have been subjected to the surface activation treatment, are brought into contact and pressed together using a press or similar machine. This process is carried out in a heated environment as necessary to strengthen the bond. In the bonding process, bonding conditions such as the heating temperature and pressing force are set according to the constituent materials of the first substrate 21 and the second substrate 22. Specific conditions include a pressing temperature of, for example, 40 to 150°C, and a bonding pressure of, for example, 0.1 to 10 MPa. This bonding process is preferably carried out while the surface activation state of the bonding surfaces of the first substrate 21 and the second substrate 22 is maintained. From this perspective, it is recommended to carry out this process within, for example, 10 minutes after the completion of UV irradiation.

After pressurizing the first substrate 21 and the second substrate 22, they may be further heated for a predetermined period of time, if necessary. As a detailed example, the first substrate 21 and the second substrate 22 may be maintained in a pressurized state for a predetermined period of time, and then the pressurized state may be released, the temperature may be raised to a predetermined temperature, and the temperature may be maintained until the desired bonding state is achieved. Here, the predetermined temperature is a temperature at which the first substrate 21 and the second substrate 22 will not deform due to heating.

After that, a cooling process is performed to obtain the microfluidic device 1, in which the second substrate 22 is partially in contact with the upper surface of the first substrate 21.

The second substrate 22 may be composed of two plate-shaped members separated at the step 33 of the first recess 3. In this case, a through-hole is formed in one of the plate-shaped members in the area where the lower space 31 is to be formed, and a through-hole is formed in the other plate-shaped member in the area where the upper space 32 is to be formed.

Next, an example of how to use the microfluidic device 1 will be described. Here, an example is shown in which the microfluidic device 1 is used to collect bile secreted from hepatocytes.

i) First, as shown by the solid arrow in Figure 9, hepatocytes are seeded in the lower space 31 of the first well 3. At this time, because the lower space 31 is recessed, it is easy to seed the hepatocytes in the lower space 31. The hepatocytes are preferably added as dispersed cells. They may also be added as cell clusters. The size of the cell clusters in this case is, for example, approximately 30 to 100 μm.

Hepatocytes placed in the first recess 3 adhere to the bottom surface 3a. The hepatocytes adhere to the bottom surface 3a so as to cover the top of the first groove 51.

ii) Next, culture medium (culture medium) is supplied to the first recess 3, and hepatocytes are cultured. As shown by the dashed-dotted arrows in FIG. 9 , culture medium is supplied from one side of the upper space 32 in the second horizontal direction D2 and discharged from the other side of the second horizontal direction D2 into the upper space 32, thereby perfusing the culture medium in the upper space 32. By providing an upper space 32 that is larger than the lower space 31 in the first recess 3, hepatocytes can be cultured in the lower space 31 while perfusing the culture medium in the upper space 32. Because the lower space 31 is recessed, the impact of the perfusion of culture medium on the hepatocytes in the lower space 31 can be reduced. Hepatocytes grow until they cover most or all of the bottom surface 3a of the first recess 3. As the hepatocytes grow, bile canaliculi (microbile ducts) are formed within the hepatocytes. Bile excreted from the bile canaliculi flows into the first groove 51.

iii) Next, as indicated by the dashed-dotted arrows in Figure 9, liquid is supplied from one of the second recesses 4, and the liquid is discharged from the other second recess 4 while bile is collected from the microchannel 5. At this time, because most or all of the bottom surface 3a of the first recess 3 is covered by hepatocytes, it is possible to largely or completely prevent the culture medium in the first recess 3 from flowing into the first groove 51. This makes it possible to collect a high concentration of bile excreted from the hepatocytes.

Although embodiments of the present invention have been described above with reference to the drawings, the specific configurations should not be considered limited to these embodiments. The scope of the present invention is indicated not only by the description of the above embodiments but also by the claims, and further includes all modifications within the meaning and scope of the claims.

The structures used in the above embodiments can be used in any other embodiment. The specific configuration of each part is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the present invention.

(1) In the above embodiment, the microchannel 5 is formed between the first recess 3 and the second recess 4, aligned in the second horizontal direction D2, and includes a plurality of holes 53 connected to the ends of the plurality of first grooves 51 in the first horizontal direction D1, but is not limited to this. For example, the microchannel 5 may include a single hole between the first recess 3 and the second recess 4 that is connected to all of the ends of the plurality of first grooves 51 in the first horizontal direction D1.

(2) The microchannel 5 may also include a plurality of third grooves formed between the first recess 3 and the second recess 4, aligned in the second horizontal direction D2, and connected to the ends of the plurality of first grooves 51 in the first horizontal direction D1.

(3) In the above embodiment, the microchannel 5 includes a plurality of second grooves 52 formed on the bottom surface 4a of the second recess 4 and aligned in the second horizontal direction D2, and the plurality of second grooves 52 are connected to the ends of the plurality of holes 53 in the first horizontal direction D1, respectively. However, this is not limited to this. For example, the microchannel 5 may include a single groove formed on the bottom surface 4a of the second recess 4, and this single groove may be connected to all of the ends of the plurality of holes 53 in the first horizontal direction D1.

(4) In the above embodiment, the first recess 3 includes a lower space 31 extending upward from the bottom surface 3a, a step portion 33 at the upper end of the lower space 31 that has a larger cross-sectional area than the lower space 31, and an upper space 32 adjacent to the upper side of the lower space 31 and whose cross-sectional area is enlarged by the step portion 33. However, this is not limited to this. For example, the first recess 3 may be a cylindrical depression without the step portion 33.

(5) In the above embodiment, the second groove 52 is formed across the entire bottom surface 4a of the second recess 4 in the first horizontal direction D1, but this is not limited to this. For example, as shown in FIG. 10, the second groove 52 may be formed up to the center of the bottom surface 4a of the second recess 4 in the first horizontal direction D1.

(6) In the above embodiment, the bottom surface 3a of the first recess 3 has a square shape, but this is not limited to this. For example, the bottom surface 3a of the first recess 3 may have a circular shape, as shown in FIG. 11. In this case, the lower space 31 has a cylindrical shape.

(7) In the above embodiment, two second recesses 4 are provided on either side of the first recess 3 in the first horizontal direction D1, but this is not limited to this. For example, as shown in FIG. 12, only one second recess 4 may be provided for each first recess 3. Note that for ease of explanation, the device body 2 is omitted from FIG. 12, and the microchannel 5 (first groove 51, second groove 52, hole 53) is shown in a simplified form (the same applies to FIGS. 13 to 17).

(8) In the above embodiment, only one first recess 3 is provided, but this is not limited to this. For example, as shown in FIG. 13, multiple first recesses 3 may be provided independently of each other along the first horizontal direction D1. In the example shown in FIG. 13, two first recesses 3 are provided independently of each other along the first horizontal direction D1, but three or more first recesses 3 may be provided.

(9) The first recess 3 and the second recess 4 may also be arranged as shown in Figure 14.

(10) The first recess 3 and the second recess 4 may also be arranged as shown in Figure 15. In the example shown in Figure 15, the second recess 4 is sandwiched between the first recess 3 in the first horizontal direction D1.

(11) Furthermore, as shown in FIG. 16, a configuration may be adopted in which a plurality of first recesses 3 and second recesses 4 are provided along the second horizontal direction D2. In the example shown in FIG. 16, two first recesses 3 and two second recesses 4 are provided along the second horizontal direction D2, but three or more of each may be provided. In this case, as shown in FIG. 16, the first recesses 3 may be configured such that adjacent lower spaces 31 are independent of each other and adjacent upper spaces 32 are connected to each other.

(12) The first recess 3 and the second recess 4 may also be arranged as shown in Figure 17. The embodiment shown in Figure 17 is a combination of the configurations of Figures 14 and 16.

1: Microfluidic device 2: Device body 2a: Upper surface 2b: Lower surface 3: First recess 3a: Bottom surface 3b: Opening 4: Second recess 4a: Bottom surface 4b: Opening 5: Microchannel 21: First substrate 21a: Concave and recessed groove 22: Second substrate 22a: Through-hole 22b: Through-hole 31: Lower space 32: Upper space 33: Step portion 51: First groove 52: Second groove 53: Hole D1: First horizontal direction D2: Second horizontal direction D3: Up-down direction

Claims (8)

a device body having an upper surface and a lower surface;
a first recess for culturing cells and a second recess for supplying or discharging a fluid, the first recess and the second recess opening on the upper surface of the device body at positions spaced apart in a first lateral direction parallel to the upper surface of the device body;
a microchannel communicating a bottom surface of the first recess and a bottom surface of the second recess,
A microfluidic device, wherein the microchannel comprises a plurality of first grooves formed at least on the bottom surface of the first recess and aligned in a second horizontal direction perpendicular to the first horizontal direction. The microfluidic device of claim 1, wherein the microchannel comprises a plurality of holes formed between the first recess and the second recess, aligned in the second horizontal direction, and connected to the first horizontal ends of the plurality of first grooves, respectively. the microchannel includes a plurality of second grooves formed on a bottom surface of the second recess and aligned in a second horizontal direction;
The microfluidic device according to claim 2 , wherein the second grooves are connected to first lateral ends of the holes, respectively. The microfluidic device according to claim 1 or 2, wherein the first recess comprises a lower space extending upward from the bottom surface, a stepped portion at the upper end of the lower space that has a larger cross-sectional area than the lower space, and an upper space adjacent to the upper side of the lower space and whose cross-sectional area is enlarged by the stepped portion. a plurality of the first recesses and a plurality of the second recesses are provided along a second lateral direction;
The microfluidic device according to claim 4 , wherein the adjacent lower spaces are independent of each other and the adjacent upper spaces are in communication with each other. The microfluidic device according to claim 1 or 2, wherein a plurality of the first recesses are provided independently of each other along the first horizontal direction. The microfluidic device according to claim 1 or 2, wherein a plurality of the second recesses are provided so as to sandwich the first recess in the first horizontal direction. The microfluidic device according to claim 1 or 2, wherein the plurality of first grooves are formed across the entire bottom surface of the first recess.